Eur. Phys. J. D 46, 453-461 (2008)
https://doi.org/10.1140/epjd/e2008-00004-8

Independent particle model of spontaneous symmetry breaking in planar π-electron systems

¹ Department of Applied Mathematics, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada
² Nuclear Physics Institute, Czech Academy of Sciences, Prague-Řež, Czech Republic

Corresponding author: ^a thiamova@scienide.uwaterloo.ca

Received: 22 August 2007
Published online: 11 January 2008

Abstract

The singlet stability of symmetry adapted (SA), restricted Hartree-Fock (RHF) solutions, and the implied symmetry breaking for several planar, π-electron systems, is investigated using the semiempirical Pariser-Parr-Pople Hamiltonian in the whole range of the coupling constant. We focus here on highly symmetric cyclic polyenes C₁₀H₁₀ and C₁₄H₁₄ and their various distorted analogues of lower symmetry, in particular on the perimeter models of naphthalene and anthracene (p-naphthalene and p-anthracene) modeling the so-called [n]-annulenes. Relying on earlier results for general systems with conjugated double-bonds, we explore the character and properties of both the SA and broken-symmetry (BS) RHF solutions for these systems and relate their behavior to those of highly symmetric cyclic polyenes and corresponding polyacenes. In this way we are able to provide a better understanding of the spontaneous symmetry breaking in these systems at the Hartree-Fock level of approximation.